For the supply or the removal of signals, connecting leads are often conductively connected with two wire conductors. During couplings of this type, in order to make contact it is necessary each time to remove or pierce the insulation layer of the two wire conductor. A multiple coupling of connecting leads results in damage to the two wire conductor. In addition, the unallowed coupling of unauthorized third parties onto the two wire conductor is easily feasible. In a telephone network utilizing conductive coupling, unauthorized parties can readily switch on. European Patent Publication No. EP-OS 0 417 542 discloses an apparatus for the inductive coupling of sending coils to a two conductor wire which largely eliminates such problems. Therein, a three-limbed ferrite core is utilized, whose yoke, for the insertion of the coupling coil or the two wire conductor is so pivotally arranged, that the two wires of the transmitting line accordingly pass through the center limb and one of the two outer limbs. For example, the coupling coil connected with the transmitting unit surrounds the center limb with several windings. For the transmission of information between two subscriber end units coupled to the transmission line, the transmitter generates a modulated high frequency signal to the primary coupling coil, which signal transforms the transformer, comprised of the coupling coil and the transmission line, and carries same, via the secondary-sided transmission line to the receiving end unit. The primary-sided perceived load Z1 of the transmitter ideally corresponds to the product of the secondary-sided contacting load Z2 and the square of the transmission ratio (N1/N2). Parallel thereto, the relatively small main inductivity of the transformer makes an appearance, which requires an amount of current which exceeds, many times, that of the transformed load or resistance Z1. The main capacity becomes particularly small if the secondary windings, formed via the transmission line, has only a few windings. The inductive coupling is thus problematic only for nonsystem-connected terminal units, which, for example, only have very low supply voltages available and which can supply only small outputs. Normally, with such terminal units only a limited range can be achieved, within which there is a satisfactory signal to noise ratio. If, for example, in order to increase the range, the output to the transmission line is increased, there is a reduction of the life span of the batteries that feed the terminal unit. In terminal units, powered by the network, a correspondingly larger dimensioned current supply unit would have to be provided.